JPS5875316A - Multiple frequency band tuning system - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Technical field to which the invention relates] This invention relates to a tuning system for a television receiver that selects one of a plurality of channels arranged in a plurality of frequency bands. Television receiver tuning systems typically employ multiple tuners, each with its own mixer, to receive signals in multiple television frequency bands. For example, the first tuner is in the VHF television station wave number band (54 to 88M).
The second tuner selects the channel of
70-890MHz). In addition to this TV receiver, you can also receive cable television (hereinafter referred to as 0ATV).
In order to receive a signal (referred to as a third tuner), it may be necessary to add a third tuner or mixer to the tuning method.

A double conversion tuning method to avoid the complexity and expense inherent in multiple tuners is used for receiving VHF and TLHF television broadcast signals, for example, in IE Transactions on, published in February 1978. e-Consumer Electronics (EEEE Transa)
tions on Consumer EEelect
ro-ni, cs) Vol. CE-24 No. 1 No. 39-4
The paper by Ash (D, L, Ash) published on page 6 “High Performance Television Receiver”
TV Receiver) J. However, there is still a need for a simple and inexpensive tuning scheme for receiving VHF, UHF and CATV signals.

[Disclosure of the invention]

The multi-band tuning method according to the present invention is based on the first broadcast band 1 and the first broadcast band 1.
The control device generates an IP multiplied signal from an RF multiplied signal belonging to the wired band 1, the second broadcasting band, and the second wired band in this order, and the tuning signal whose magnitude is determined by the frequency of the selected channel is transmitted to the control device. an RF multiplied signal corresponding to a selected channel in a first tuned band including a first broadcast band and a low frequency portion of a first wired band in response to the tuned signal; The second filter selects the RF multiplied signal corresponding to the selected channel in the second tuning band, which includes the high-wavenumber portion of the first wired band, the second broadcast band, and the second wired band. be done. A first filter is enabled if the selected channel is within a first tuning band, and a second filter is enabled if the selected channel is within a second tuning band, respectively, by the selection device.

[Embodiments of the invention]

In the double conversion tuning method shown in Fig. 1, the TlHF antenna human power 1
OSvHF antenna input 30A1 CATv input 30B
The television signal received is supplied to the guiplexer 20 as described below. This method uses frequency conversion (transition)
is performed twice, so it is a multiple conversion tuning method. In the United States, each television signal has a number shown in Table 1. Table', male.

It belongs to the wave number band.

Each channel is assigned a bandwidth of approximately a MHz in the frequency spectrum and has an image carrier at a frequency 1.25 MHz above the lower frequency limit of the bandwidth of its assigned channel. When a particular channel frequency is referred to in the following description, that frequency corresponds to the frequency at which the image carrier of the selected television channel is converted in that particular portion of the tuning scheme.

Figure 2 shows the frequency spectrum for channel frequencies of various television frequency bands in the United States (al K shows L, -VHF band 202s H-V HF band 206%D
I (For F band 210, the broadcast signal strength is 10μ, for example.
Although the received signal amplitude is shown by multiple levels showing that it can vary between V and room'V, the strength change in the received CATv signal aS is very small and the MB-O
ATV band 204, SB-OAT V band 208 vc
As shown in the figure, it is usually 1 to 6 mV.

Figure 2 (tel is 44% of the filter in Figure 1 as described below)
36.14vc respectively indicate the associated radio frequency (RF) low band, high band and UHF band. The first intermediate frequency (IF)' between the usB-CATV band and the tlHF-TV band (F) is chosen to be 415.75 MH2, thus approximately 42
Since it is outside the radar band of 0 to 450 MHz, it is unlikely to be interfered with by other signal sources. The second F is a standard television F of 45.75 MH'Z.

The present invention is not limited to the various broadcasting i-bands and wired bands currently in use in the United States; for example, it is also possible to send signals in the broadcasting band through a single wired line.

When the broadcast television channel is in the VHF band, it is VHF'-social flow ii in Figure 1.

Antenna 10 to tlHF band frequency selection tuning filter 1
4 to the input 20A of the diplexer, an O filter 14 receives a tuning potential VT from line 140 and passes preferentially the frequency corresponding to the selected television channel between its output 14A and output 14B. .

FIG. 3 shows a frequency selective attenuation characteristic curve 3 corresponding to the selection of a television channel with a relatively low UHF frequency ft.
Indicates 00. The filter 14 is the low frequency part 3 of the curve 300.
02 exhibits low attenuation and relatively large attenuation in the high frequency section 304. The signal near the selected channel frequency ft is transmitted with a bandwidth of 3.
As shown by the peak around that frequency of 06, it is passed preferentially. Bandwidth is defined as the distance between the intersection of the characteristic curve with the dashed line 308, which indicates 3 dB higher attenuation in the passband. The characteristic curve 300' corresponds to the characteristic curve 300 when the selected channel frequency ft is a relatively high frequency ft. In the case of the circuit of the filter 14 shown in FIG. 4, the frequency ft corresponds to the TlHF channel, but when one frequency ft' corresponds to the UHF channel 83vc, the bandwidth 306/ is considerably increased. Next, one embodiment of the filter 14 will be described.

The first frequency of 416MHz is t[(1 because it is close to the F band).
Reduce the level of all 16MHz signals. This useless signal is generated externally or leaked from the first IF section.
This level reduction prevents unnecessary signals of the first F frequency from being applied to the F circuit. The top 12 exhibits a high-pass frequency characteristic of 500 as shown in FIG.
Lowest frequency of HF band (approx. 470MHz) K corresponding frequency f. Higher frequency almost unattenuated portion 50
4 and a low frequency portion 502 with large attenuation, 1 and an intermediate frequency f as shown by a portion 506 of the characteristic curve
It shows maximum attenuation near i.

Output 14A of filter 14 and diplexer 200Å force a
During oA the signal is fed to OHF amplifier 16. Amplifier 1at;t II 14-15d in the HF frequency range
It exhibits a gain of B and has an input/output impedance of about 1500. The amplifier 16 has its operating voltage, that is, the band switching voltage VB3 (
Approximately 18■) is missing, so it does not work.

V) Television signals in the TF band and 0ATV band are divided into low and high tuning bands as follows. This signal is 9 to 1
Tuning over the above frequency range with a range of 3 to 1 or more is not practical due to the limited range of the voltage variable capacitance diode. Between the M B'L CAT■ band and the H-VHF band, the range (approximately 1 to 4M
(in Hz) requires a tuning range of approximately 3.25 to l for the low band. The apparatus of this invention is MB-C! as shown in FIG. In order to divide the tuning band at a frequency of approximately 15oMHz within the ATV band, there are 1 high and 3 low tuning bands each.
Contains frequencies in the range below 1:1.

The selection of the low to high tuning band frequency is also influenced by the design of the filters 36 and 44. In filter design, it is more difficult to obtain a specified narrow frequency band at high frequencies than at low frequencies.1
In addition, it is more difficult to obtain a constant bandwidth with a filter that can be tuned over a wide frequency range.It is more difficult to minimize 0 distortion and adjacent channel interference (0) than when the signal amplitude range is small (such as the ATV signal). It is necessary to narrow the filter bandwidth when the signal amplitude varies widely (such as a VHF television broadcast signal).The boundary between the low and high bands is M
B. - Since xao MHzK in the CATV band is set, L-VHF and H-VHF broadcast television signals with large variations are both in the band of each tuning system.Therefore, the filter used in the tuning method of the present invention17)l Since satisfactory performance can be obtained by wave number division, there are fewer problems with the design requirements for the tunable filter used therein.

Television signals in the VHF and 0ATV frequency bands are supplied to the diplexer 20vc as follows. In FIG. 1, switch S1'A is set to f! 1fBC-AK
II f and the VHF antenna 30A or the rat trough 32 signal is applied), and when it is tilted to the position 0A-A, the 0ATV signal is applied to the trap 32 from the input terminal 30B.

Trap 32 is similar to trap 12 described above with respect to FIG. 5, but with a maximum attenuation range 502 at a frequency f corresponding to the lowest frequency to be received (VHF channel 2). (approximately 54 MHz) - second intermediate frequency fi (approximately 46 MHz)
z). Trap 32 sends the signal through circuit point 32B to low band (54~150 MH2') and high band (150 MH2')
~402MH2). If the selected channel is in the high band, the signal VB2 is applied to the switch 34% 38 to make it conductive (closed) and the high band filter 36 is inserted between the circuit points 32B and 140A. is in the low band, the signal VBz is switched to switch 4.
2s 46 and conducts it, and a low pass filter 44 is inserted between circuit points 32Bs4OA.

The high-band tuning filter 36 has a high-pass frequency selection characteristic 60 such that greater attenuation occurs in a relatively lower frequency portion than in a relatively high frequency portion 604, as shown in the sixth vA.
0 and thus not only selects the frequency corresponding to the selected channel ft, but also rejects signals of lower frequencies, in particular signals in the low tuning frequency band. Song M60
Bandwidth for 0 is shown for -5dB@. When a channel with a high frequency is selected, the bandwidth of the filter 36 becomes wider.

Characteristic 6001IIi Corresponds to characteristic 600 when the frequency ft of the selected channel is a relatively high frequency ft/.If the filter 36 is tuned so that f corresponds to MB-OATV4 channel Fvc, 1 band II! 606
is about 18 MHz s fl, ' is S B - CA
When tuned to correspond to the T V f channel w+17, the bandwidth 6o6/ is approximately 4o MHz.

The low band filter 44 has a low pass frequency selection characteristic 300 as shown in FIG.
＼The higher the frequency channel is selected, the wider the bandwidth becomes.◇For example, the bandwidth 3 when ft corresponds to VHF channel 2.
06 is about a MHz, but ft/ is M B -OA
The bandwidth 306/ when corresponding to T V +-Janne AEEvc is approximately 20 MHz. Therefore, filter 4
In addition to selecting the frequency corresponding to the 4H channel ftK, it also blocks signals at much higher frequencies, especially signals at the first intermediate station wave number in the higher tuning band.

1st Fl! J's VHF amplifier 40J'J circuit point 40A1
7) A signal is supplied to the input 20B of the diplexer 20, which is substantially the same as the tlHF amplifier 16 described above, but its operating potential VBr2 is 12% of the diode D1.
4 is supplied from a diode "OR" circuit containing 1 amplifier 4°, so that when the low tuning band is selected a channel in the high tuning band is selected, the band switching voltage VBI or FiVB2! The difference is that TJT (when a channel in the F band is selected) does not receive an operating potential. When the KUHF channel is selected, circuit point 4OA is connected to the diplexer. 2o input 20B.

The diplexer 2o in Figure 1 has VH connected to its human terminal 20A.
1 from the F band signal path and the human power terminal 20BKVHF band and C
It receives RF multiplied signals from each of the AT■ bands and combines these signal paths to generate an RF signal at its output terminal 2ocvc. In the diplexer 2o, the circuit includes a high-pass filter (HPF) 22 that couples the input terminal 20A to the circuit point 24 and a low-pass filter (L) that couples the circuit point to the output terminal 200.
The input terminal 20B (including PF) 26 is connected to the circuit point 24 by a plurality of cascaded low-pass filters 28.

The mixer 5o outputs one local oscillation frequency signal from the output goc of the RF signal diplexer to the amplifier 52 via a circuit point 52.
The RF multiplied signal of the selected channel frequency is converted into a first intermediate frequency signal of about 416 MHz (ie, first frequency conversion).

U.S. Patent Application No. 294,131, filed Aug. 19, 1981, discloses a suitable circuit configuration for diplexer 2o and mixer 5o.

A relatively high level frequency signal in the range of 18 dBm is supplied to the frequency mixer 50vC.
Road point 5! Driving the zero mixer 50, which maintains an impedance of approximately 500 AK, with such a high level frequency signal allows the relative strength of the RF multiplied signal from the diplexer 2o to be increased without increasing distortion.

For the reasons mentioned above, it is desirable to choose a relatively high intermediate frequency of approximately 416 MH2, which is a high drive level for the mixer 50, and to eliminate distortion within the mixer 50. It is desirable to choose the circuit gain to be sufficient to keep the receiver noise figure within acceptable limits. In this case, the bandwidth of each of the filters 14A36% 44 can be relatively wide in the double-conversion tuning scheme to obtain equivalent distortion and noise performance, compared to the narrow bandwidth required in the single-conversion tuning scheme. This advantage allows the bandwidth of the filter to widen with the frequency of the selected channel, as described above.

This first F signal is then amplified by a F amplifier 60.

This amplifier 60 has a frequency of about 12 MHz at an intermediate frequency of 416 MHz.
It may include a two-part input filter tuned with a bandwidth of H2 and a three-part output filter tuned with a bandwidth of about 10 MHz to an intermediate station wavenumber of <+16 MHz. The amplifier F signal at the output 62A of this amplifier is frequency mixed with the 370 MHz frequency signal from the local oscillator 64 by a wave number mixer 62 &l in a second frequency conversion to produce a 46 MHz normal F signal.

is provided to output 68.

The tuning controller 7o outputs a tuning potential vT according to the channel selection.
and band switching potential VBISVB2% MB3 are generated.

The tuning potential vT is generally indicated by the broken line 2 as shown in Figure 2 (cl).
It varies between a low level of approximately 1.5V, indicated by 20, and a high level of approximately 24V, indicated by dashed line 222. If the selected channel is in the low tuning band, the potential vT is VHF channel 2
becomes the low value of point 224 when is selected, and MB-OAT
The high value of point 226 occurs when V channel E is selected. Also, if the selected channel is in the high tuning band, the vine potential VT is also MB-CA TV.
When T v channel * le W + 17 is selected, it will have a high value of 230 points. Similarly, the potential VT is DHF channel 14
When is selected, it becomes a low value of point -232, and LIE(F
The high value of point 234 occurs when channel selection is selected. The band switching signals vB1, MB2, and MB3 are used only when the channel of the corresponding band is selected (fd in Fig. 2), (
e) ~ (Power characteristics 240.250s As shown at 260, it is at a high level of about 18V, but when other channels are selected, it is at zero level.

3 tunable voltage controlled i-part oscillators (VCO) AA・56
%58 is provided to generate local oscillation frequency signals in three tuning bands. This means that depending on the same tuning potential V'TK the frequency of a particular oscillator (54% 56% 58) works well with its associated filter (14% 36S4)
The purpose is to be able to track the frequency tuning of 4). The frequency range of the frequency signal supplied from the circuit point 52B to the amplifier 52 is shown in the table below.
are configured to operate only when the selected channel is within the frequency band related to each oscillator, with the band switching potentials VB1\VB2 and MB3 as their operating potentials.

Next, regarding FIGS. 4 and 7, filter 14136.
A suitable configuration of 44 will now be described.

The tlHF bandpass filter 14 in FIG.
Inductor L402, L406 s L between 4As 14B
It is a double-tuned low-pass filter with "high side inductive coupling" provided by series connection of 40BzL410 and L414. C408 works as a DC blocking capacitor whose AC impedance can be ignored in the UHF band. Inductor L404
X'L406 has an input 14A impedance of approximately 50
Similarly to 1, inductor L410 s L412 also works as a tapped inductor structure to keep the in-vehicle value of output 14B at about 500. Input/output inductor L402, L4141d
Helps maintain a substantially constant bandwidth over a wide tuning range of filter 14. Capacitor C is connected to inductor Laoa.
404 are connected in parallel and resonate at about 100100O.

Variable capacitance diodes CD42% are connected from both ends of the tuned circuit Laos-C4o4 to ground via coupling capacitors C402 and C406, which have extremely low impedance at the frequency of the television signal passing through this filter 14.
Upward frequency tuning is performed by the CD44. terminal 1
The tuning potential VT of aC is applied to the diodes CD42%CD44 through insulation resistors R402 and R404, respectively, to change their capacitances.

This potential VT varies in the range of approximately 1.5 to 24 V in the tJHF channels 14 to 83.

FIG. 7 is a detailed diagram of the switches 34% 38% 42% 44 and the tunable filter 36% 44. switch 34
When the band switching voltage VB2 is applied via the RF choke L702, the television signal is applied from the line 32B to the input 36A via the DC blocking capacitors C702 and C704 when the P/N diode SI)yg becomes conductive.

Resistor R702 is □S when the high band channel is selected.
Controls the forward current flowing through D72. During this time, the PIN diode 5D74 is reverse biased by the potential across the resistor R702, but when a channel in a band other than the high band is selected, the X diode SD74 is reverse biased by the potential across the resistor R702.
It is forward biased by VBI applied through 84 or VH2 applied through diode D78. The forward current flowing through this diode D78 is determined by the resistor R702K, and the potential difference between both ends of the diode 5D determines the forward current flowing through the diode D78.
72 vc reverse bias is applied. Resistor R704 creates a feedback path when 5D74 is reverse biased. Capacitor C706 is a DC blocking capacitor that provides a low impedance connection at television frequencies between diode 5D72 and ground when diode SD74 is conductive.

The switch 38 is of the same type as the switch 34 and becomes conductive or non-conductive at the same time. Switches 42 and 46 are also similar to switch 34, but conduct only when a low band channel is selected. Switch 34% 38% 42% 46vc
The following table shows the corresponding elements that perform the same function in
2＼ Series connection of CD74 and shunt inductance L70
6. It shows a high-pass characteristic due to the "low side" inductive coupling of L708 and L710. 1) The part including the capacitor 0708) and the inductor L708 also shows a high-pass characteristic tuned to block low-band signals. .

The tuning potential vT of the terminal aaC changes to the variable capacitance diode CD72% CD? according to the reverse bias applied through the resistors 706 and 708, respectively. Variable tuning is achieved by varying the respective capacitances of 4'. The capacitance of CD72 resonates with the inductor L7045L706) cD'
y4's 0 low band tunable filter 44 which resonates with L710s L712 is across the r high side inductive coupling and is similar to the t]'E(F filter 14 described above)0 inductor L
276 and capacitor 0728 are tuned to resonate at approximately 200 MHz to block high band signals. This - frequency also changes the tuning potential of terminal aaC ■T to resistor R724%
R) Voltage variable capacitance diode CD'ya through 26
Even lower 1 lvc by applying to s CD7B
be synchronized. Capacitors C726 and C730 provide a relatively low impedance path at television frequencies between the respective cathodes of diodes CD76 and CD78 and ground. Inductors L722 and L724 are inductors L'730s L
Like 728, it works as a tapped inductor structure.

This invention is limited only by the scope of the claims.
Possible changes are possible. For example, television receivers are usually VHF.
'y antenna 3oA and 0ATV connection 3. When using either oB, the programming of the vHF channel is usually 0.
Since it is performed by the ATV power supply, it is assumed that both of them will not be used, so Shimanuichi Sl is shown as a mechanical switch, but if you wish to receive fully automatic reception, S engineering A
can be replaced by a relay or P-N diode controlled by a band-switching voltage or diplexer (remove F amplifier 16 and VHF amplifier 40 and add one line to line 20C between diplexer 20 and mixer 50)
If an amplifier is inserted, a PIN diode switch similar to switch 34 can be placed in its place.

. FIG. 8 shows a particular variation that is desirable when the first intermediate frequency is approximately 416 MHz. The broadcast television signal for VHF channel 12 has a picture carrier of approximately 2C15 MH2 and an audio carrier of approximately 210 MHz. It is desirable to attenuate these carrier waves because the second harmonic of these carrier waves as well as the signal of the sum of their frequencies is close to the intermediate frequency. Therefore, the inductor L706 explained in FIG.
are selectively combined to form a trap except when channel 12 or adjacent channels 11, 13 are selected.

The inductor L806 is arranged so that its coil is coupled together with the two turns of the coil of the inductor L706 closest to the ground point G, 1 so that the capacitance C5ol becomes L
reflected by the transformer coupling between aO2 and TJ706\
The effect of being in series with the part of L706 farthest from the ground point G is shown. This combination acts as a series trap circuit,
Approximately 20 d at 210 MHz tuned to channel 12
B, 2o gives approximately 1 odB attenuation at 5 MHz. A portion of the operating voltage +V generated by the voltage divider including resistors R80L and R802 is applied to the anode of switch diode 5D801. The upper connection point of C801 and LaO2 is grounded via a capacitor C802 whose impedance can be ignored at television frequencies.
803 also has the cathode of 5D801 grounded.

When receiving a broadcast, switch S, which is the second pole of switch A in Figure 1, is moved to position BC-B, and voltage +V is applied to the cathode of 5DaOl via switch S2 and resistor R803. to reverse bias. 5D801
When 0801 is reverse biased, 0801 is coupled as described above. Channel 11.12% When any of 13 is selected, 1, Sg changes from position IN to position NK and becomes 5D8
The cathode of 01 is grounded and this 5D801 is forward biased. This results in C801 essentially shorting this 5D80
1 N 5D803% 5DE102 is grounded through negligibly low impedance and connected to the trap circuit C described above.
ao1- Disable L706 O When receiving wired, S I
B" to position 0A-BK and trap circuit Cool -
O to emasculate TJ706 in the same way

[Brief explanation of drawings]

FIG. 1 is a block diagram illustrating one embodiment of the invention; FIG. 2 is a block diagram illustrating one embodiment of the invention; FIG. Curve Design No. 4
FIGS. 7 and 8 are circuit diagrams illustrating circuits useful in the tuning scheme of FIG. 36...Second filter means X44...First filter means 170n11 control means) 42.46.34X3
8. ...Filter selection means. Patent applicant: RCSNY Corporation Representative: Tetsu Shimizu and two others Procedural amendment (method) December 9, 1981 1, Indication of case Patent application 143969 No. 5'7-143969 No. 2, Name of invention Multi-frequency band Synchronization method 3, relationship with the case of the person making the amendment Patent applicant address New York, United States of America 1002
0 New York Rockefeller Frasa 30 names
(757) RCSNY Corporation 4, Agent 5, date of amendment order: November 12, 1980 (dispatch date: November 3, 1982)
0 days) 6. "Detailed description of the invention" column of the specification subject to amendment. 7. Edit pages 5, 17, 18, and 21 of the specification of the contents of the amendment (no changes to the contents). Attached document specification (No. 5, page l'7.18.21) 1 line
Each channel is assigned a bandwidth of approximately 6 MHz in the frequency spectrum and has an image carrier frequency 1.25 MHz higher than the lower frequency limit of the bandwidth of its assigned channel. When a particular channel frequency is referred to in the following description, that frequency corresponds to the frequency at which the image carrier of the selected television channel is converted in that particular part of the tuning scheme. The frequency spectrum for channel frequencies of various television frequency bands in the United States is shown in Figure 2). L
-4HF band 202, T(-VE(F band 206, UI(F
For band 210, the broadcast signal strength is, for example, 10240.
250 and 260 are at a high level of about 18V as shown, but when other channels are selected, they are at zero level Cζ. 3 tunable voltage controlled local oscillators (VCO) 54.56
．． 58 is provided to generate local oscillation frequency signals in three tuning bands. This means that, depending on the same tuning potential VT, the frequency of a particular oscillator (54, 56, 58) will be adjusted by its associated filter (14, 36, 44).
This is to make it possible to track the frequency tuning of. The frequency range of the frequency signal supplied to amplifier 52 from circuit point 52B is shown in the following table. Oscillators 54, 56, 58 each have a band switching potential VBI
. It receives VB2 and VB3 as its operating potential and operates only when the selected channel is within the frequency band related to each oscillator. Next, regarding FIGS. 4 and 7, filter 14.36.
A suitable configuration of 44 will now be described. The UHF band filter 14 in FIG.
Inductor L402, L406, L408 between A and 14B
, L410, and L414 are connected in series. C408
acts as a DC blocking capacitor that can ignore AC impedance in the UHF band. Inductor L404, L406
acts as a tapped inductor structure to keep the impedance of input 14A at approximately 50Ω, and similarly inductor L41
0, L412 is also conductive only when the output 14B is input. The corresponding elements performing similar functions in switches 34, 38, 42, 46 are shown in the following table.

Claims (1)

[Claims] (11 first broadcast band 1 first wired band) In a multi-frequency band tuning method that generates an RF signal from an RF signal belonging to a second broadcast band and a second wired band in this order, 1
control means for generating a tuning signal whose magnitude is determined by the frequency of the selected channel; and a first tuning including a low frequency portion of the first broadcast band and the first wired band in response to the tuning signal. a first filter means for selecting an RF multiplied signal corresponding to a channel selected in a band; a second filter means for selecting an RF multiplied signal corresponding to a selected channel in a second tuning band including at least a low frequency portion of the band;
said first filter means is operable when the selected channel is in said first tuning band; and (9) said second filter means is operable when the selected channel is in said second tuning band. 1. A multi-frequency band tuning method, comprising: a filter selection means for selecting a filter to obtain a filter.